1. Field of the Invention
This invention relates to a seat suspension that will permit quick adjustment of the vertical height of the seat and more particularly will permit the seat to be adjusted from its lowest to an intermediate or highest position without the need for the operator to hold a latch mechanism controlling the seat height adjustment in a nonengaged position.
2. Description of the Prior Art
The prior art discloses many different types of suspension systems that mount a vehicle seat, such as a tractor seat or the like, to float within a vertical range of movement on a vehicle in a manner permitting the selection of any one of several vertical seat height positions within the range of floating movement. This selection enables the operator to set the vertical height of the seat relative to the vehicle to accommodate the operator's height.
Prior art seat suspension systems typically comprise a stationary support in the form of a vertical tower that is mounted on a track mechanism which allows the tower to be adjusted fore and aft relative to the vehicle steering wheel. An intermediate frame is mounted on the tower by an adjustable main spring suspension system for vertical floating movements relative to the tower. The suspension system may include a shock absorber for damping the floating movements. A seat support frame that carries an operator's seat is mounted on the intermediate frame and is normally biased to one position relative to the intermediate frame by a secondary spring connected between the intermediate frame and the seat support frame. Provision is made so that any one of several vertical positions of the seat support frame relative to the intermediate frame can be selected.
U.S. Pat. No. 3,861,637, issued Jan. 21, 1975 to Jacques Albert Huot DeLongchamp, discloses this general type of seat suspension system. In this prior art seat suspension, the seat support frame is releasably interlocked with the intermediate frame by means of a single withdrawable horizontal locking bolt that passes from the center of the seat support frame through one of a series alignable holes in the intermediate seat support frame.
The use of a horizontal lock bolt causes the operator significant difficulties when attempting to select a comfortable seat height within the range of floating movement. For example, when the seat is in its lowermost position relative to the intermediate frame and the operator desires to raise the sea height relative to the intermediate frame, the operator must withdraw the lock bolt and to do so, the operator must remove his weight from the seat. This weight removal results in the main spring of the suspension causing the now unloaded seat to move upward to the top end of its vertical range of travel and also results in the secondary spring automatically raising the seat support frame upward relative to the intermediate frame. Thus, when the operator removes his weight and releases the lock bolt, the seat will move to its maximum vertical height and the operator now has no convenient reference point to indicate how much the seat support frame should be lowered relative to the intermediate frame. DeLongchamp shows four seat height position holes and with the seat at its uppermost position, the operator must guess in which hole the locking bolt should be placed to provide a proper height setting. As a practical matter, the operator sits down and applies downward pressure on the seat, guesses when to release the locking bolt and then when it enters a hole, applies his full weight to the seat to cause it to move down to its working range where the operator can determine if the height setting is correct.
Thus, the setting of the seat height is a repetitive hassle and requires the operator to engage in a time-consuming, annoying, and repetitive select-and-try type of procedure. This is true even when the operator knows exactly in which intermediate hole the bolt must be placed to achieve the correct height setting because there is no way for the operator to actually know when he has the lock bolt inserted into the desired hole other than actually permitting the lock bolt to insert itself in a hole and then applying full weight to the seat to test the actual seat height.
Another disadvantage is that the lock bolt cannot be locked into a selected position. This means that the lock bolt can be withdrawn when the seat is unoccupied. If this occurs, the stored force of the secondary spring will raise the seat support frame relative to the intermediate frame to an upper limit position, and when the operator reoccupies the seat he must again go through the repetitive select-and-try seat height selection procedure.
A further disadvantage of known seat suspensions concerns lateral stability of the lower rear portions of the operator's seat. In the prior art, this lower rear portion of the seat is stabilized by the single centrally located locking bolt. During operation, especially on uneven terrain, the tractor will tilt in lateral directions and cause the operator's weight to repetitively shift from side to side. In such conditions, the single center locking bolt tends to act as a central pivot allowing the lower portion of the seat to twist.
Present seat suspensions do not solve these problems. Specifically, known seat suspensions do not provide a simple rugged seat suspension wherein the operator can quickly and easily adjust the seat height to a desired vertical position without the need to activate a release mechanism and which provides lateral stability for the lower rear portion of the operator's seat.